Lymphocyte activating factor activity in the serum and cerebrospinal fluid of patients with multiple sclerosis.

Serum and cerebrospinal fluid (CSF) from patients with multiple sclerosis (MS), patients with other (non-inflammatory) neurological diseases (OND), patients with non-inflammatory non-neurological diseases, and normal controls were assayed for lymphocyte activating factor (LAF) activity by thymocyte costimulation. LAF activity was detected in normal control sera, which did not differ significantly in this respect from MS or OND patient sera. Not were there significant differences by stage of MS (chronic progressive MS, MS in relapse and MS in remission) or between MS patients and the non-inflammatory non-neurological controls. Almost all the CFSs assayed presented lower values than did the corresponding sera. Serum and CSF after fractionation showed no significant increase in LAF activity except in the 2 MS patients in remission. From these data it may be assumed that LAF activity does not necessarily correspond to the clinical phase of MS. The possible role of LAF activity as a marker of MS progression has yet to be determined.